Yo-yos most commonly are made from wood or from a molded plastic as the principal material of construction. Yo-yos made from different materials present a different feel to the yo-yo player, some players preferring the feel of one over the other. Some yo-yos have been made from metal which presents still another feel that may be preferred by some players. Few metal yo-yos have been commercialized, however, and, as to those, their availability has been limited possibly because the typical construction for such yo-yos is costly and is substantially more than that of a more conventional yo-yo made from plastic or wood. In one prior art construction, the metal yo-yo may be formed from aluminum by machining the yo-yo halves that will be assembled to form the yo-yo body in a milling machine from solid round aluminum bar stock. The entire yo-yo half is formed, in one piece, from the round aluminum bar stock. The end of the bar stock is milled to form the outer face of the yo-yo half by removing an annular region of material, leaving a center hub and a peripheral rim. The peripheral contour of the yo-yo half also may be milled, as may be the inner face of the yo-yo half. The milled piece then is cut-off from the round bar stock to a thickness appropriate for the yo-yo half. The inner face of the yo-yo half then is machined further by drilling and tapping a center hole along the central axis of the yo-yo half to accept the threaded end of an axle by which two yo-yo halves will be joined. After machining, the yo-yo halves then are individually polished and finished. Such one-piece yo-yo halves are made individually in a labor intensive process that is wasteful of material, all of which adds to the cost of the yo-yo.
Also among the desirable features of a yo-yo, especially for those users who wish to perform complex string tricks, is to provide a wide peripheral entry to the string slot between the yo-yo halves. Yo-yos having such a wide entry sometimes are referred to as having a "butterfly" configuration. While incorporating a butterfly configuration in a plastic injection molded yo-yo is simply a matter of configuring the mold for the yo-yo halves, the fabrication of a butterfly yo-yo from metal, using the prior art milling technique described above, presents additional difficulties in milling the peripheral surfaces as well as the inner surfaces of the yo-yo halves. Such milling results in still further waste of material and additional labor and other expenses attendant to finishing the surfaces of the yo-yo halves. The milled one-piece metal yo-yo involves a machining process that can be expected to leave marks and other irregular surface regions that should be finished to a smoother surface in order to accept a desired finish, such as anodizing or finishing graphics. The milled metal yo-yo halves do not lend themselves to mass finishing but, instead, must be finished individually, adding further to the cost of the yo-yo.
Also, among the significant features of a yo-yo is the manner in which the yo-yo engages the string to catch the string to initiate the rewinding and retrieval of the yo-yo. The feel and responsiveness to the player's retrieval command (slackening the string to relieve it of all tension) is, in part, a matter of personal preference and may depend on the types of tricks to be performed. It is desirable for the yo-yo to catch the string in a consistently responsive manner in order to enhance the player's control over the yo-yo. In some cases, it may be preferred for the yo-yo to have a "hair trigger" response in which very slight manipulation of the string is required to cause the string to become caught in the yo-yo to effect the retrieval. Others may prefer a less sensitive trigger reaction in which a more distinct manipulation is necessary in order to initiate the retrieval. Regardless of the degree of responsiveness, it is important that the response is consistent so that the player can best control the yo-yo. A starburst pattern of radial ribs on the inwardly facing surface of the yo-yo halves has been used in order to enhance the ability of the yo-yo to catch the string when tension on the string is momentarily released. The use of a starburst pattern may tend to increase the immediacy of the response to the retrieval command. While the starburst pattern of ribs may facilitate catching of the string, some yo-yo players may not favor the use of ribs because they may not provide the desired feel and degree of responsiveness when retrieving the yo-yo.
It would be desirable to provide a metal yo-yo embodying a construction and method of manufacture that would reduce substantially the cost and ease of manufacture while providing a metal yo-yo with desirable characteristics, including the ability to form a butterfly yo-yo. It also would be desirable to provide a yo-yo configured to provide a desired feel and consistency during retrieval, for those players who may prefer not to use a yo-yo having the starburst rib configuration.